* src/newgrp.c: Use a %lu format and cast group and user IDs to

	* src/newgrp.c: Use a %lu format and cast group and user IDs to
	unsigned long integers.
	* src/newgrp.c: The ID argument of audit_logger is an unsigned
	int.
	* src/newgrp.c: Ignore the return value of signal() (the signal
	handlers are assumed to be the default one and are restored
	later).
	* src/newgrp.c: Do not checl if a pid_t is < 0, check if equal
	to (pid_t)-1.